Reporter-gene assays are used to study eukaryotic gene expression. Dual genetic reporters are commonly used in transient transfections of cultured cells to minimize experimental variability caused by differences in cell number, viability or transfection efficiency. One plasmid containing the experimental reporter gene (coupled to a regulated promoter) is cotransfected with a second plasmid containing a control reporter gene (coupled to a constitutive promoter). Bioluminescent reporter systems using firefly and Renilla luciferases are widely used as co-reporters because both assays are easy and sensitive. Previously, luciferase reporter assays have been “flash” assays that must be read within seconds of reagent addition and require integrated injectors in the luminometer. (See Maxline App Note #39). Recently, Promega introduced a Dual-Glo Luciferase assay system for high-throughput analyses. The signals are stable for 2 hours after reagent addition and integrated injectors are not necessary. This application note demonstrates the effectiveness of using this system and the excellent detection limits achievable.